passive preamp matching
Well its pretty simple and I reccomend it with no reserves!! You do need to have the right numbers for it to work properly: First: 1-Amplifier Input sensitivity (Volts) 2-DAC (or cd player) output voltage The Dac output must be higher than the amps sensitivity, usually a DAC will have 2 volt output and the input sensitivity will be around 0.5 volts: Thats why it works so good!! Second: 1- Amplifier input impedance (ohms) 2- DAC (or cd player) output impedance (ohm) This is the tricky part: You need at least 10 times lower impedance on the DAC than the Passive preamp and another 10 times lower impedance on the passive than the input impedance of the amp: Lets say your DAC has 50 ohm output impedance, and your amp has 15k ohm (15,000 ohm) input impedance; You will be OK with a 1k preamp (such as EVS), But a 10k preamp will probably sound funny! My DAC has 50 ohm output and my Amps have 1 meg ohm input. The best sound I got was the 1K, it could work with 10k or even 100k but the volume was very hard to control (very little movement would blast the speakers) I had to go down from 100k to 10k to 5k to 1.2k and eventually settled at 1k, let me tell you the difference between 1.2k and 1k is big!!! It was fun all the way! There are 3 types of passive preamps: 1-Carbon Volume pot based (Alps, Luminous Audio, etc.) 2-Resistor loaded (several types) (Placette, Dact, Goldpoint, etc.) 3-Transformer Volume control or TVC (Promitheus, Bent, Django etc) I personally like the Resistor based ones better (I tried most of them). Hope this helps |
Jameswei Read your post. Just wanted to know if it was a risk to use a TLC-1 with a B&K 2140 through 1m XLO cables. I wont have the option of changing the preamp in the near future. Also planning to use one of the tape outs to power a sub? The souuce will be a Music Hall cd 25.2. Speakers are very efficient DIY. (dont turn the volume past 10:00) on my present preamp |
A very strong second to the Placette recommendation. Absolutely fantastic! Like finally opening a slightly dirty window to breath fresh air and see the view unobstructed. Hey, they should use me for ad copy, eh? My setup doesn't conform to the requirements suggested above. My amp input impedance is only 10K. The output of the Placette is 2K which is only five times lower, as opposed to the ten times suggested above. I don't know the output of my Muse Model 2 plus dac that is doing duty as the front end, and how that might come into play, but the system works perfectly with no quirkiness at all. Raising the volume is a bit strange as the high volumes that I'd normally associate with severe distortion, do not have any apparent. The volume goes up and down as smooth as silk. In my system it is very engaging, crystal clear, and exhibits no dynamic shortcomings, nor any compromises at the extremes. Bass response is outstanding, and much better than the Cary tube pre I had been using as a pinch-hitter in this system. In other words, it has no weaknesses in my system that I can tell. Oh, also, I'm using 2 meter IC's between Placette and the amp and 2 meters between source and Placette. Length of IC is supposedly another issue to be aware of. It's a wonderful way to go if it works in your system. I'd consult with Guy at Placette if you have specific concerns (or with whatever company you choose to go with). Marco |
Marco, What amp(s) are you using? Your setup (at least the Placette and input impedence of the amp) sounds remarkably similar to mine. I have the Placette and simply love it also and the only thing that has tempted me otherwise is to audition the Placette active, but I'm very happy with the passive. My amps are the Odyssey Mono Extremes with input impedence of 10K ohms. And my IC's from the Placette to the amps are, like yours, 2 meters. As the to downside of this setup---none to my ears. I hear no problems with dynamics or anything else. Of course, maybe I got no ears.... |
"Am I right to assume that the pre won't be a correct match with the power?" No the preamp will work just fine, you are in the 10 times rule all over, anyway the buffer in an active stage with no gain that is supposed to match impedance, thats why it has a lower output impedance than the input. I am sure the Music hall should have about 250 ohms output or less, so you should be fine....its not passive though. If you get a chance call Guy from Placette audio he is one of the nicest guys around and try one of his passives out!! If you dont like it you can give it back! Too bad he doesnt make a 1k unit! All the best |
No, you're not. According to thisreport by J Atkinson at Stereophile, the TLC-1 you're considering should do OK with yr 33,2k amp -- if a bit uncertain at very low volumes. You may want to try it at low volume level (say 8-9 o' clock). Again, however, on paper it should be fine. BTW, it seems this device offers less than unity (i.e. full output lower than input). |
What amp(s) are you using? Your setup (at least the Placette and input impedence of the amp) sounds remarkably similar to mine. Well, that's because it IS similar to yours. I'm using the Placette with the Odyssey Dual Mono, which is very similar to your amps, though not identical. Front end is a Muse Model Two Plus either via a transport or a PC using a Waveterminal U24. Wires are Truthlink, Quicksilver and Tara going from source to speakers. Speakers are Silverline SR-17 (V3). The story with this system may be interesting to others so I'll go on a bit more. I had been using the Portal Audio Panache integrated in this, my secondary system. I'd owned that amp for a bit more than a year and was delighted with it. It has amazing midrange clarity and drive and I'd always found it very engaging and easy to listen to. There was only one area where I could occasionally find fault with it and that was in taking an authoratative grasp on the low end. Recently that obsessive audiophile itch to change something came up and I had to scratch it. Reluctantly I sold the Panache to try something with more power that might take charge of the low end better. I chose the Odyssey Dual Mono, which I was somewhat familiar with the sound of since I'd heard it a few times in my friend's various systems (in fact he was the one selling his to me). I put it into my system with my Cary SLP-50A preamp borrowed from my SET system. Viola! Bass to write home about. But wait, where's that amazing midrange I'd gotten used to. The clarity had been replaced by a warmth. Though it did not sound bad at all, and I did like it right away, I still found myself longing to have the clarity and sweetness of the Panache midrange back. It was my friend, Peter, who'd sold me the amp, who suggested I check into passive alternatives. I did a bit of research and found a good deal on a Placette and decided to give it a try. It made perfect sense since the Panache has a passive gain stage as well. The idea worked like a charm. I was worried having read many threads about careful matching of components, and didn't think my numbers would be right. I also knew, having bought the Placette used, that I could easily sell turn it around at little or no loss. It worked! There was my midrange back in all it's glory, with the bass I was looking for and shimmering highs to boot. The experience of putting it in place an listening the first time was truly like opening up a window. Peter came over and had a listen and liked it a whole lot too. He was very familiar with the sound of the Panache in that room and knew just what I was looking for. And there it was. Startling clarity, balance and presence. Like almost all SS systems I've ever heard it has a flatter soundstage than tubes, and especially compared to SET, but it does have many nice qualities that tubes do not. Drive, detail, and clarity come to mind. Meanwhile Peter and I have ordered a Sonic Euphoria PLC to do a comparison with in our various systems. I have not even tried the Placette downstairs with the SET system, but I'm predicting it might work great since the input on those amps are 300K! That's my passive story, and I'm stickin' to it. Marco |
Keroo - This ad for your CD player would indicate it has a 2.5 V output. If detail and clarity are your passwords then you're barking up the right tree. "Transparency" is the word that comes up over and over in Placette comments, and it certainly has that in spades...well, invisible spades! Marco |
